The present invention generally relates to fasteners and driving systems. More particularly, the present invention relates to a high speed, high torque screw fastener having faceted or undercut walls such that a corresponding driver bit is locked in engagement therewith when torque is applied to the driving bit.
The prior art is replete with various forms of designs of drive systems where typically a fastener head includes a recess while a driver bit is provided with a complimentary shaped projection for insertion into the recess. One common such system, as illustrated in FIG. 1, for fasteners, such as screws and bolts, is the formation of a generally uniform slot 2 formed across the diameter of the fastener head 4. The driving blade 6 of a regular or flat screwdriver or driving bit which has a diameter at a free end or tip thereof which is slightly less than the diameter of the slot 2 is inserted into the slot and torque applied thereto in order to turn and drive the fastener.
However, this arrangement has several drawbacks. As can be seen in FIG. 1, the points of engagement 8 between the driver blade 6 and the fastener head 4 are at opposite extreme ends of the driver blade 6. It is very easy for the driver blade 6 to slip out, sometimes referred to as cam out, of engagement with the slot 2 during operation. This is particularly the case when applying high torque or attempting to drive the fastener with increased speed. Moreover, in high torque or high speed situations, the driver blade 6 and/or the walls of the slot 2 can be damaged.
There are other well known fastener drive systems which include different configurations of the recess formed in the fastener head. For example, such systems include a cruciform-type system often referred to as Phillips, internal hex, internal square, internal star and Torx™ configurations. However, these configurations also experience cam out and the edges of the recesses or the drill bits can become deformed or otherwise damaged in high torque or high speed applications. Thus, these screw head and driver systems require lower twisting torque because higher torque would cause the fastener head or driver to deform or break. This can limit the size of the fastener or the type of fastener head used, and whether the fastener is countersunk into a material.
For example, conical or wedge shaped screw heads are more likely to “pull through” the material, such as wood, drywall and other soft materials. Although a common or pan head screw having a flat underside surface would be preferable, existing fasteners and drive systems are unable to withstand the high torque necessary to countersink such fasteners in the material.
In another example, hex head screws or bolts are typically used in metal fastening applications in which flat or conehead screws or bolts, which can be countersunk, would be preferred, but cannot be used simply because the weakness of the screw head and driver head systems currently used do not permit them to be tightened to the required high tightening torques. The screw or bolt head, or the driver head, will break under these higher torques.
In addition, existing fasteners and drive systems require the operator to apply strong downward forces on the tool to maintain the contact between the fastener head and the driver as the fastener is being installed or removed, which can result in broken tools and fasteners, as well as operator discomfort and possible long-term injury.
The use of power tools to install common wood screws or machine bolts has become widespread. Many industries utilize automatic-feed tools, in which a supply of screws or bolts on a strip or in a magazine is automatically delivered to the power tool, or totally automated factory assembly line systems, in which the screw or bolt is automatically fed and installed by tooling. In the construction industry, because of the speed of the powered tooling and the benefits of using screws, and with the increasing use of metal studs to replace conventional wood studs, screws are replacing traditional nails. However, as described above, current screw head and driver design severely limit the speed and the amount of twisting force or torque that can be used in installing or removing these screws or bolts with powered tooling.
Accordingly, there is a continuing need for an improved fastener and driver system which reduces or eliminates slip out or cam out. There is also a continuing need for such a fastener and driving system which can withstand high speeds and high torque applied thereto. There is further a need for such a fastener and driving system which can be used in connection with power tools, including automatic-feed tools, and which does not require large downward forces. The present invention fulfills these needs, and provides other related advantages.